The so-called “green comet” will pass closest to Earth on Wednesday and Thursday, but you’ll probably need binoculars to see it in San Diego.
Officially named Comet C/2022 E3 (ZTF), it was discovered by astronomers using the wide-field survey camera at Caltech’s Zwicky Transient Facility on Mount Palomar in March.
“This particular object was spotted because of its motion in a sequence of images taken by ZTF,” Physics Professor Tom Prince told the Caltech Magazine. “At the time it was discovered, it was not known to be a comet. That came later after follow-up observations by many telescopes worldwide.”
It’s dim, but you can see it in binoculars or a small telescope. Look high in the north sky, above the north star, Polaris.
Analysis of the comet’s orbit around the Earth shows that it last appeared 50,000 years ago, when Neanderthal hunters and giant mastodons roamed the planet.
The green color is due to the presence of diatomic carbon — two-atom carbon molecules — in the comet’s tail that react with gases in the solar wind. But with just binoculars or a small telescope, you probably won’t see green — only white.